The distribution device is a key component of any typical top charging installation because proper charge distribution is crucial for reactor operation.
In the iron-making industry, a charging system commercially known by the name bell less Top® has found widespread use for charging blast furnaces. This system typically includes a distribution device with a distribution chute that is rotatable about the vertical furnace axis and pivotable about a horizontal axis for distributing bulk material on the stockline as desired. The device has a mechanism for rotating and pivoting the distribution chute according to the desired charging profile. Systems of this type have been disclosed for example in international patent application WO 95/21272 and in U.S. Pat. No. 5,022,806; U.S. Pat. No. 4,941,792; U.S. Pat. No. 3,814,403 and U.S. Pat. No. 3,693,812. By rotating the chute about the vertical furnace axis and by varying the inclination of the chute, burden in bulk can be directed to virtually any point of the charging surface. Besides many other advantages, this type of distribution device enables a wide variety of charging profiles due to its versatility in distributing the burden on the charging surface. Accordingly, it requires highly developed equipment, in particular as regards the mechanism for rotating and pivoting distribution chute.
A currently less widespread alternative is a so-called cardan-type or gimbal-type distribution device. This type has a tubular distribution spout that is suspended in cardanic manner so as to be pivotable about two generally perpendicular axes of which one is typically horizontal. Since cardan-type devices have no revolving spout support that rotates full turns (>360°), they theoretically facilitate construction of the drive equipment and, if cooling of the chute is desired, of corresponding cooling equipment.
An early example of a cardan-type distribution device is disclosed in U.S. Pat. No. 4,243,351. The spout is suspended on a supporting fork, which is rotatably supported on its first end to provide for pivoting about a first horizontal axis. The spout is pivotally suspended on the pronged second end of the support fork to provide for pivoting the spout about a second axis perpendicular to the first axis. A first actuator is connected to the first end of the support fork for pivoting about the first axis. The support fork further carries a transmission mechanism for transmitting action of a second actuator from the first end of the supporting fork to the pivoting suspension of the spout on its second end. A variety of similar designs have been proposed in patent literature, e.g. in: U.S. Pat. No. 3,972,426; U.S. Pat. No. 4,306,827; U.S. Pat. No. 4,525,120; IT 1103916; IT 1126248 and DE 2 649 248. Examples of suitable drive arrangements for pivoting the spout are described in more detail e.g. in U.S. Pat. No. 4,306,827 and U.S. Pat. No. 4,889,004 and U.S. Pat. No. 4,889,008. In such devices, the support of the spout is a generally fork-shaped member as described above that carries both the spout and a transmission mechanism connected to the second actuator for pivoting about the second axis. The fork-type support being designed for significant loads and torques, it has comparatively large size and heavy weight thus increasing the moment of inertia on the first axis, i.e. the main suspension axis.
Designs with reduced moment of inertia on the main suspension axis have been proposed in Japanese patent application JP 58 207303 and in European Patent EP 1 833 999. In these devices, a conventional cardan construction with two ring-shaped gimbal members supports the spout. A drive arrangement with two similar transmission mechanisms connects the cardan suspension, in particular the gimbal member that has both pivotal degrees of freedom, to respective actuators. Compared to the aforementioned fork-type designs, the gimbal members are compact and less heavy since they do not carry the load of any transmission mechanism. A drawback of designs according to JP 58 207303 and EP 1 833 999 resides in the actuators used in their drive arrangement. As opposed to drive configurations according to U.S. Pat. No. 4,306,827 and U.S. Pat. No. 4,889,004 and U.S. Pat. No. 4,889,008, they use linear actuators i.e. hydraulic cylinders for actuation of each of the two degrees of freedom. As will be understood, such design implies that each actuator is permanently oscillating for achieving typical charging patterns that require circular or spiral motion of the spout outlet. As a result, a device according to JP 58 207303 and EP 1 833 999 is inherently subject to a certain degree of actuator outage and consequent repair.